Swelling of the Optic Disk in the Retina in Dogs

Papilledema is the term given to a non-inflammatory swelling of the optic disk. Although generally asymptomatic by itself, this condition is most often visible with an ophthalmoscope as the borders of the optic disk will be raised in all but the earliest stage of papilledema. There are a number of underlying disorders and diseases that can cause papilledema to develop, but all of them will be characterized by an increase in intracranial pressure. Treatment is generally focused on reducing the pressure in the cranium, generally by addressing the underlying disorder.

A non-inflammatory swelling of the optic disk caused by an increase in intracranial pressure is known as a papilledema. Left untreated this condition can cause blindness.

Papilledema in the earlier stages is generally asymptomatic on its own, although left untreated the optic disk will atrophy and partial or total blindness can develop. Signs relating to the increased intracranial pressure that causes the papilledema may be concurrently observed. Pupillary responses to light will be normal, which helps to differentiate papilledema from optic neuritis. 

Types 

Papilledema Stages

Stage 0

• Normal Optic Disc  

Stage 1

• Very Early Papilledema: Obscuring of the border of the disc
• No elevation of the disc borders
• Light grayish halo with a gap when viewed with indirect ophthalmoscopy

Stage 2

• Early Papilledema: All borders are obscured, and will show elevation
• Complete peripapillary halo is observable

Stage 3

• Moderate Papilledema: In addition to obscured borders on the optic disk there is an increased diameter of the optic nerve head
• One or more segments of major blood vessels are obscured
• Peripapillary halo will now have an irregular outer fringe with finger-like extensions

Stage 4

• Marked Papilledema: The entire head of the nerve is elevated
• Total obscuration of a segment on the disc with a major blood vessel has occurred

Stage 5

• Severe Papilledema: Dome-shaped protrusions and expansion of the optic nerve head backward
• Peripapillary halo is narrow and smooth
• Optic cup is obliterated

Excessive intracranial pressure may lead to a non-inflammatory swelling of the optic disk known as papilledema. There are many disorders and diseases that can increase the intracranial pressure in your canine. These can include:

• Brain tumor
• Distemper
• Glaucoma
• Granulomatous meningoencephalitis
• Hepatic encephalopathy 
• Hydrocephalus
• Lesion of the central nervous system (CNS)
• Mycoses (Systemic)
• Postoperative ocular hypotony
• Toxoplasmosis
• Trauma
• Uveitis

Your veterinarian will most likely use an ophthalmoscope to examine the eyes of your dog. The optic nerve head will be swollen or raised in appearance when viewed and a peripapillary halo may also be observable. In most cases of papilledema will present bilaterally and retina itself will be normal. The pupillary response to light will be tested to see if the eyes are normally reactive, and intracranial pressure will be measured using a device that is placed inside the head. An electroretinogram may be used to investigate the function of the retina and an MRI or CT scan might also be recommended. It is important to differentiate papilledema from similarly presenting disorders. Some of the disorders your veterinarian will want to rule out will include:

Psuedopapilledema -Similar to papilledema in appearance but is caused by excessive myelination of axons at the optic nerve-head.

Optic neuritis -Inflammation of the optic nerve. May occur separately or in conjunction with papilledema. This disorder is differentiated by pupillary response. In papilledema alone the pupils will respond normally to light, but the pupillary response with optic neuritis is fixed.

SARDS -A disease that causes sudden blindness in dogs. The electroretinogram will detect normal function for either papilledema or optic neuritis, but flat function in SARDS.

Tests such as the electroretinogram and tests for intracranial pressure will require anesthetic and therefore may require hospitalization. The treatment for papilledema will then be determined based on the underlying cause of the disorder. 

A lesion of the central nervous system known as a brain neoplasm is a commonly found cause for the increase in the intracranial pressure. In these cases, surgery will usually be attempted to remove all or part of the lesion, depending on its placement and size. A biopsy of these tissues will help determine which treatment plan will best mitigate the growth. Radiation therapy is often successful in managing these neoplasms as well. 

Any infections that would affect the brain will be addressed with the appropriate medications and corticosteroids might be recommended, especially if the disorder is associated with an inflammatory disorder as well.

If surgery was required a calm and quiet environment will best help your pet recover. Make sure that you complete all medications given by your veterinarian, even if symptoms seem to clear up. This is to ensure that no reoccurrences of the underlying conditions will follow treatment. If the optic disk was badly atrophied your dog will be blind in the affected eye or eyes. 

Blindness in one eye usually causes a minimal impact to life quality. You will want to be aware that your dog may startle and snap more easily when approached on its blind side. Papilledema usually is bilateral, meaning that it will have an effect on both eyes. If your dog has lost vision in both eyes they can still lead a full and satisfying life with just a few considerations, such as blocking access to potential dangers like stairs or pools and not rearranging objects in their environment without showing them the new arrangement.